Asymmetric ring electrode cap and matched welding device thereof

Abstract

The invention discloses an asymmetric ring electrode cap, which abandons the traditional design of uniform spherical electrodes on two sides, and adopts an asymmetric ring electrode structure, specifically, the diameter of the welding end face of a thin plate side electrode cap is 6-14mm, the curvature radius is 40-100mm, the thin plate side electrode cap is provided with three rings, the inner ring contains a conical pit, and the cross section of the middle ring is an isosceles trapezoid; the diameter of the welding end face of the thick plate side electrode cap is not smaller than the thin plate side and not larger than 14 mm, the curvature radius is not smaller than the thin plate side and not larger than 100 mm, the thick plate side electrode cap is also provided with three rings, the inner ring comprises a conical pit, and the section of the middle ring is an equilateral triangle. The ring structure parameters of the two electrode caps are accurately designed to meet the welding requirements of plates with different thicknesses, and the welding quality and efficiency are improved. The method is particularly suitable for resistance spot welding of materials such as aluminum workpieces with large thickness ratios.

Description

Technical Field

[0001] The invention relates to the field of resistance spot welding, and in particular to an asymmetric ring electrode cap and a matching welding device thereof, which can effectively control the deviation of the resistance spot welding nugget of an aluminum workpiece. Background Art

[0002] Resistance spot welding is a complex process involving multivariable coupling. It plays an important role in the automotive manufacturing industry, especially in the field of steel connection. However, with the increasing global attention to energy conservation and emission reduction and the vigorous development of the new energy vehicle industry, automobile lightweighting has become a key way to alleviate energy shortages and environmental pollution problems. The application of aluminum alloys is one of the effective ways to reduce the weight of automobiles. Among the many aluminum alloy connection technologies, resistance spot welding has become the preferred method for realizing large-scale mass production connection of aluminum alloy parts due to its unique advantages such as high efficiency, low cost, high flexibility and no increase in weight.

[0003] However, the types and thicknesses of aluminum alloy plates used in different parts of the car often vary greatly. In some cases, there is even a need for welding with a large thickness ratio (such as 3:1 to 4:1). Resistance spot welding under such a large thickness ratio faces a severe challenge: the molten core is often excessively concentrated on the thick plate side, while almost no molten core is formed on the thin plate side, which directly leads to a decrease in the strength of the welded joint, thus posing a potential threat to the overall safety of the car.

[0004] Patent CN109014535A discloses a spot welding method for aluminum plates of unequal thickness. By setting different arcs of the electrode cap end face to change the effective contact area between the electrode cap and the plate, the current density and the depth of penetration are changed, and the heat distribution of the plates of unequal thickness is effectively balanced, thereby improving the problem of nugget deviation. However, a side effect that cannot be ignored is that the higher current density accelerates the pitting process of the electrode, resulting in the need for frequent grinding of the electrode, which in turn affects the overall efficiency of resistance spot welding.

[0005] Patent CN111014923A discloses a resistance spot welding device and method for plates of unequal thickness. This method uses a small-section annular cross-section electrode on the thin plate side and adds ceramic material inside the electrode ring, while a circular-section copper electrode is used on the thick plate side. During welding, since the welding end face of the small-section annular cross-section electrode is much smaller than the circular-section copper electrode, the current density on the thin plate side is much greater than that on the thick plate side, which increases the heat dissipation on the thin plate side. The filling of ceramic material can also reduce the heat loss of the thin plate, thereby causing the resistance spot welding nugget to shift to the thin plate side. Although this method also improves the nugget shift by increasing the current density on the thin plate side, it also faces the problem of premature pitting of the electrode, which has a potential impact on welding efficiency. Summary of the invention

[0006] The purpose of the present invention is to provide an asymmetric ring electrode cap and its supporting welding device, which can effectively weld aluminum alloy parts of unequal thickness, offset the molten core to the thin plate side, increase the molten core on the thin plate side, and make the molten core meet the requirements of aluminum alloy resistance spot welding standards.

[0007] The technical solution of the present invention is as follows:

[0008] An asymmetric ring electrode cap is characterized in that it is composed of a thin plate side electrode cap (11) and a thick plate side electrode cap (12) that are used in conjunction with each other.

[0009] The thin plate side electrode cap comprises an electrode cap body, a thin plate side surface (3) and a thin plate welding end surface (4), wherein the diameter of the thin plate welding end surface (4) is d2 and the radius of curvature is R1, wherein 6mm≤d2≤14mm, 40mm≤R1≤100mm;

[0010] The thick plate side electrode cap comprises an electrode cap body, a thick plate side surface (8) and a thick plate welding end surface (5), wherein the diameter of the thick plate welding end surface (5) is d3 and the radius of curvature is R2, wherein d2≤d3≤14mm and R1≤R2≤100mm;

[0011] Wherein, the thin plate welding end face (4) is the welding end face corresponding to the thin plate side, and the thick plate welding end face (5) is the welding end face corresponding to the thick plate side;

[0012] The thin plate welding end face (4) has three rings, wherein the inner ring has a structure in the shape of a conical pit in the middle, the conical pit has a depth of h1, a diameter of d6, a diameter to the inner ring of d7, and satisfies 0.05mm≤h1≤1mm, 0.05mm≤d6≤d7≤14mm; the middle ring has a height of h3, a ring width of d4, a ring spacing of d5, the cross-sectional dimensions of each ring are equal, the cross-sectional shape is an isosceles trapezoid, the hypotenuse is 45°, and 0.05mm≤h3≤1mm, 0.05mm≤d4≤d5≤1mm;

[0013] The thick plate welding end face (5) has three rings, wherein the middle of the inner ring has a structure in the shape of a conical pit, the depth of the conical pit is h2, the diameter is d10, the diameter to the inner ring is d11, and it satisfies 0.05mm≤h2≤1mm, 0.05mm≤d10≤d11≤14mm; the height of the middle ring is h4, the ring width is d8, the ring spacing is d9, the cross-sectional dimensions of each ring are equal, the cross-sectional shape is an equilateral triangle, and 0.05mm≤h4≤1mm, 0.05mm≤d8≤d9≤1mm.

[0014] Furthermore, the diameter of the thin plate welding end surface (4) is d2, the diameter of the thick plate welding end surface (5) is d3, and 6mm≤d2≤d3≤14mm.

[0015] Furthermore, the radius of curvature of the thin plate welding end surface (4) is R1, the radius of curvature of the thick plate welding end surface (5) is R2, and 40mm≤R1≤R2≤100mm.

[0016] On the other hand, the present invention also provides a welding device for welding aluminum workpieces using the above-mentioned asymmetric ring electrode cap, which is used for welding thin-plate aluminum workpieces (15) and thick-plate aluminum workpieces (14), and is characterized in that it includes:

[0017] A first welding gun arm (9) and a second welding gun arm (10);

[0018] A thin plate side electrode cap (11) mounted on the first welding gun arm (9);

[0019] A thick plate side electrode cap (12) mounted on the second welding gun arm (10);

[0020] The thin plate aluminum workpiece (15) is made of deformed aluminum alloy and has a thickness of 0.5-2.5 mm; the thick plate aluminum workpiece (14) is made of cast aluminum or deformed aluminum alloy and has a thickness of 2.5-6 mm.

[0021] During welding, the welding gun arm is operated to make the thin plate side electrode cap (11) and the thick plate side electrode cap (12) closely fit the thin plate aluminum workpiece (15) and the thick plate aluminum workpiece (14), and pressure is applied to clamp them, so that the fitting parts of the two aluminum workpieces are melted to form a molten core (16).

[0022] The present invention also provides a resistance spot welding method, which comprises:

[0023] (a) A pair of the above-mentioned electrode caps are provided, the electrode cap for welding end face 4 is placed on the thin plate side, and the electrode cap for welding end face 5 is placed on the thick plate side.

[0024] (b) Pre-pressing stage: the electrode caps are placed on both sides of two stacked aluminum workpieces of unequal thickness, without constraining the positive and negative electrodes, and pre-pressing is performed, the positive electrode is moved closer to the aluminum alloy plate until the welding end face is tightly fitted to the plate, and a pressure of 2500-6000N is applied, and the pre-pressing duration is 200-2000ms;

[0025] (c) Power-on welding stage: a welding current is applied, the effective value of the welding current is 15-60 kA, and the power-on time is 80-200 ms.

[0026] (d) Cooling stage: After the welding current stops, the electrode caps remain pressed against both sides of the plate for 30-400ms, and the molten metal solidifies to form a weld.

[0027] The mechanism of the present invention is as follows: taking welding of two layers of aluminum alloy workpieces of unequal thickness as an example, for symmetrical electrodes without the special design, during welding, due to the smaller thickness of the thin plate, the heat dissipation of the electrode at the thin plate is better than that of the electrode at the thick plate, and the body resistance of the thick plate is much greater than that of the thin plate, so the thin plate generates resistance heat by relying on the contact resistance between the two plates, while the resistance heat of the thick plate is generated by the body resistance and the contact resistance. It can be seen from the comprehensive that the heat generated by the thick plate is much greater than that of the thin plate, while the heat dissipation is much less than that of the thin plate, which leads to uneven heat on both sides of the thin plate and the thick plate, and the molten core shifts to the thick plate side after welding. When the specially designed electrode cap is used during welding, due to the asymmetric ring design on both sides, the area of ​​the thin plate side that first contacts the electrode is smaller than that of the thick plate, which increases the heat generation on the thin plate side during welding, maintains a higher temperature, and the molten core shifts to this side plate. That is, the molten core is controlled to shift to the thin plate side. Increase the melting depth on the thin plate side.

[0028] Technical effect: Since the contact area between the contact surface 4 and the thin plate 6 is smaller than the contact area between the contact surface 5 and the thick plate 7 during welding, the heat generated at the thin plate can be increased, so that the molten core can extend to a certain depth at the thin plate, so that the molten core depth at the thin plate meets the resistance spot welding standard.

[0029] Compared with the prior art, the present invention has the following beneficial effects:

[0030] 1) The present invention designs a pair of asymmetric ring electrode caps to weld thin plate and thick plate aluminum workpieces respectively. This design enables the electrode cap to better adapt to aluminum workpieces of different thicknesses, ensuring stability and reliability during the welding process.

[0031] 2) The difference in shape and size between the thin plate welding end face and the thick plate welding end face helps to control the offset of the molten core during the welding process, which can optimize the performance of the welded joint, improve the welding quality and reduce welding defects.

[0032] 3) By setting ring structures of different shapes and sizes on the welding end face of the electrode cap, as well as features such as conical pits, the welding current and heat can be transferred more effectively, thereby improving welding efficiency and quality. At the same time, it helps to reduce defects such as spatter and cracks during welding.

[0033] 4) The device for welding aluminum workpieces with asymmetric ring electrode caps realizes stable welding of aluminum workpieces of different thicknesses by installing asymmetric electrode caps on the thin plate side and asymmetric electrode caps on the thick plate side through the first welding gun arm and the second welding gun arm respectively. At the same time, the device also has ordinary electrode caps, which can be flexibly switched and used as needed, improving the flexibility and applicability of the device. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings in the following description are only some embodiments of the present invention. For ordinary technicians in this field, other alternative implementation methods can be obtained based on these drawings without paying creative work.

[0035] Figure 1 An embodiment using an asymmetric ring electrode cap is shown.

[0036] Figure 2 express Figure 1 One embodiment of a partial elevation view cross section.

[0037] Figure 3 express Figure 1 Outline dimensions of the middle contact surface 4 and the contact surface 5

[0038] Figure 4 A partial side view showing an aluminum alloy workpiece during resistance spot welding.

[0039] Figure 5 A schematic diagram showing actual current output during a resistance spot welding process according to one embodiment.

[0040] Figure 6 Represents the cross-sectional view of the weld nugget with a plate thickness ratio of 1:2.5 for a symmetrical spherical ring electrode.

[0041] Figure 7 Represents the cross-sectional view of the weld nugget with a plate thickness ratio of 1:3 for a symmetrical spherical ring electrode.

[0042] Figure 8 This is a cross-sectional diagram of the weld nugget with a plate thickness ratio of 1:2.5 for the new asymmetric spherical ring electrode.

[0043] Fig. 9 This is a cross-sectional diagram of the weld nugget with a plate thickness ratio of 1:2.5 for the new asymmetric spherical ring electrode.

[0044] Fig.10 This is a cross-sectional diagram of the weld nugget with a plate thickness ratio of 1:2.5 for the new asymmetric spherical ring electrode.

[0045] Fig.11 This is a cross-sectional diagram of the weld nugget with a plate thickness ratio of 1:3 for the new asymmetric spherical ring electrode.

[0046] In the accompanying drawings, the symbols are as follows:

[0047] 1-Electrode cap cylinder

[0048] 2-Cooling water return tank

[0049] 3-Side of the thin plate electrode cap

[0050] 4-Welding end face of thin plate

[0051] 5-Welding end face of thick plate

[0052] 6- Thin sheet aluminum workpiece

[0053] 7-Thick plate aluminum workpiece

[0054] 8-Thick plate side electrode cap side

[0055] 9, 10-Welding gun arm

[0056] 11-Thin plate side electrode cap

[0057] 12-Thick Plate Side Electrode Cap

[0058] 13-Ordinary electrode cap

[0059] 14-Welding thick aluminum workpieces

[0060] 15-Welding thin aluminum workpieces

[0061] 16-Welding nugget DETAILED DESCRIPTION

[0062] The present invention will be further described below in conjunction with the examples and drawings. It should be understood that these examples are only used to illustrate the present invention and are not intended to limit the scope of the present invention. In addition, the drawings are schematic diagrams, and therefore the device and apparatus of the present invention are not limited by the size or ratio of the schematic diagrams.

[0063] Example 1: Asymmetric Ring Electrode Cap

[0064] This embodiment provides a pair of asymmetric ring electrode caps, which are particularly suitable for resistance spot welding of aluminum workpieces with large thickness ratio. Figure 1 As shown, it includes an electrode cap designed for the thin plate side and an electrode cap designed for the thick plate side. The electrode cap on the thin plate side is composed of a thin plate electrode cap body, a thin plate side surface 3 and a thin plate welding end face 4, wherein the diameter of the thin plate welding end face 4 is d2, and the radius of curvature is R1. Correspondingly, the electrode cap on the thick plate side includes a thick plate electrode cap body, a thick plate side surface 8 and a thick plate welding end face 5, wherein the diameter of the thick plate welding end face 5 is d3, and the radius of curvature is R2. The end face 4 of the thin plate welding electrode cap corresponds to the welding end face on the thin plate 6 side, and the end face 5 of the thick plate welding electrode cap corresponds to the welding end face on the thick plate 7 side. The thin plate side welding end face 4 and the thick plate side welding end face 5 are different in shape and size to adapt to aluminum workpieces of different thicknesses and to realize the offset control of the molten core, as shown in FIG. Figure 3As shown, the diameter of the thin plate welding end face 4 is d2, the diameter of the thick plate welding end face 5 is d3, and they satisfy 6mm≤d2≤d3≤14mm. The curved radius of the thin plate welding end face 4 is R1, the curved radius of the thick plate welding end face 5 is R2, and they satisfy 40mm≤R1≤R2≤100mm.

[0065] The thin plate welding end face 4 and the thick plate welding end face 5 are different in shape and size to adapt to aluminum workpieces of different thicknesses and to achieve the offset control of the molten core. Three rings are processed on both welding end faces, and there is a conical pit in the middle of the inner ring. For the thin plate welding end face 4, the depth of the conical pit is h1, the diameter is d6, the diameter to the inner ring is d7, and it satisfies 0.05mm≤h1≤1mm, 0.05mm≤d6≤d7≤14mm. The height of the ring in the thin plate welding end face 4 is h3, the width of the ring is d4, the distance between the rings is d5, the cross-sectional dimensions of each ring are equal, the cross-sectional shape is an isosceles trapezoid, the hypotenuse is 45°, and it satisfies 0.05mm≤h3≤1mm, 0.05mm≤d4≤d5≤1mm. For the thick plate welding end face 5, the depth of the conical pit is h2, the diameter is d10, the diameter to the inner ring is d11, and it meets 0.05mm≤h2≤1mm, 0.05mm≤d10≤d11≤14mm. The height of the middle ring of the thick plate welding end face 5 is h4, the width of the ring is d8, the distance between the rings is d9, the cross-sectional dimensions of each ring are equal, the cross-sectional shape is an equilateral triangle, and it meets 0.05mm≤h4≤1mm, 0.05mm≤d8≤d9≤1mm.

[0066] In a preferred embodiment, the diameter d2 of the thin plate side welding end surface is 8-12 mm, the diameter d3 of the thick plate side welding end surface is 8-12 mm, the curvature radius of the thin plate side welding end surface is 40 mm, and the curvature radius of the thick plate side welding end surface is 50 mm.

[0067] Embodiment 2: Welding device and welding process

[0068] like Figure 4 As shown in FIG. 2 , this embodiment also provides a device and a welding process for welding aluminum workpieces using an asymmetric ring electrode cap. The device includes a first welding gun arm 9, a second welding gun arm 10, a thin plate side electrode cap 11, a thick plate side electrode cap 12, and a common electrode cap 13 (spare). The objects to be welded include welding a thick plate aluminum workpiece 14 and welding a thin plate aluminum workpiece 15, wherein the welding thin plate aluminum workpiece 15 is a deformed aluminum alloy with a thickness of 0.5-2.5 mm; the welding thick plate aluminum workpiece 14 is composed of cast aluminum or a deformed aluminum alloy with a thickness of 2.5-6 mm.

[0069] The welding process is as follows:

[0070] ① Before welding, the electrode cap does not touch the aluminum workpiece;

[0071] ② During welding, the welding gun arm is operated to make the two electrodes closely fit the thin plate aluminum workpiece 14 and the thick plate aluminum workpiece 15, and pressure is applied to clamp them so that the fitting parts of the two aluminum workpieces are melted to form a molten core 16.

[0072] ③ The welding parameters can be adjusted according to the actual situation, including the pre-pressing stage (duration 200-2000ms), the power-on welding stage (welding current effective value 15-60kA, power-on time 80-200ms) and the cooling stage (duration 30-400ms).

[0073] Example 3

[0074] like Figure 6 The example shows the use of common symmetrical electrodes and the Figure 4 The welding device in a Figure 5 The cross-sectional morphology of the nugget after resistance spot welding of 5754 deformed aluminum alloy with a thickness of 0.95 mm and AlSi10MnMg cast aluminum alloy with a thickness of 4.0 mm with the welding parameters shown. It can be seen from the figure that there is almost no nugget on the thin plate side.

[0075] like Figure 7 The example shows the use of common symmetrical electrodes and the Figure 4 The welding device in a Figure 5 The cross-sectional morphology of the nugget after resistance spot welding of 5754 deformed aluminum alloy with a thickness of 0.95 mm and AlSi10MnMg cast aluminum alloy with a thickness of 4.0 mm with the welding parameters shown. It can be seen from the figure that there is almost no nugget on the thin plate side.

[0076] Example 4

[0077] like Figure 8 The symmetrical ring electrode cap with upper and lower welding end faces both being welding end faces 5 is shown. Figure 4 The welding device in b and Figure 5 The cross-sectional morphology of the nugget after resistance spot welding of 5754 deformed aluminum alloy with a thickness of 2.0 mm and AlSi10MnMg cast aluminum alloy with a thickness of 5.0 mm with the welding parameters shown. It can be seen from the figure that there is almost no nugget on the thin plate side.

[0078] like Fig. 9 The symmetrical ring electrode cap with upper and lower welding end faces both being welding end faces 5 is shown. Figure 4 The welding device in b and Figure 5 The cross-sectional morphology of the nugget after resistance spot welding of 2.0 mm thick 5754 deformed aluminum alloy and 6.0 mm thick AlSi10MnMg cast aluminum alloy with the welding parameters shown in the figure. It can be seen from the figure that there is almost no nugget on the thin plate side.

[0079] Example 5

[0080] like Fig.10 The asymmetric ring electrode cap is shown in FIG. 4, which uses the thin plate side welding end face as welding end face 4 and the thick plate side welding end face as welding end face 5. Figure 4 The welding device in b and Figure 5 The cross-sectional morphology of the nugget after resistance spot welding of 5754 deformed aluminum alloy with a thickness of 2.0 mm and AlSi10MnMg cast aluminum alloy with a thickness of 5.0 mm is shown in the figure. It can be seen from the figure that more nuggets melt toward the thin plate side.

[0081] like Fig.11 The asymmetric ring electrode cap is shown in FIG. 4, which uses the thin plate side welding end face as welding end face 4 and the thick plate side welding end face as welding end face 5. Figure 4 The welding device in b and Figure 5 The cross-sectional morphology of the nugget after resistance spot welding of 5754 deformed aluminum alloy with a thickness of 2.0 mm and AlSi10MnMg cast aluminum alloy with a thickness of 6.0 mm is shown in the figure. It can be seen from the figure that more nuggets melt toward the thin plate side.

[0082] The present invention also provides a resistance spot welding method, comprising the following steps:

[0083] (a) providing a pair of the above-mentioned asymmetric ring electrode caps placed on both sides of the thin plate and the thick plate, the two welding end faces have different curvatures, and the specially designed ring electrode caps are provided;

[0084] (b) Pre-pressing stage: the electrode caps are placed on both sides of two stacked aluminum workpieces of unequal thickness, without constraining the positive and negative electrodes, and pre-pressing is performed, the positive electrode is moved closer to the aluminum alloy plate until the welding end face is tightly fitted to the plate, and a pressure of 2500-6000N is applied, and the pre-pressing duration is 200-2000ms;

[0085] (c) Power-on welding stage: a welding current is applied, the effective value of the welding current is 15-60 kA, and the power-on time is 80-200 ms.

[0086] (d) Cooling stage: After the welding current stops, the electrode caps remain pressed against both sides of the plate for 30-400ms, and the molten metal solidifies to form a weld.

[0087] The asymmetric ring electrode cap and its welding device and method provided in the embodiment of the present invention abandon the traditional design of uniform spherical electrodes on both sides and instead adopt an asymmetric ring electrode structure, which realizes effective offset control of the molten core during resistance spot welding of aluminum workpieces and significantly improves welding quality and efficiency.

[0088] Although the embodiments of the present invention have been shown and described above, the above embodiments are exemplary and cannot be understood as limiting the present invention. Within the scope of the claims of the present invention, adjustments to different implementations without conflicting adjustments all fall within the protection scope of the present invention. Within the scope of the present invention, the above-mentioned technical features of the present invention and the technical features specifically described below (such as the embodiments) can be combined with each other to form a new or preferred technical solution. Due to space limitations, they will not be described one by one here.

Claims

1. An asymmetric ring electrode cap, characterized in that: It is composed of a thin plate side electrode cap (11) and a thick plate side electrode cap (12) used in conjunction with each other. The thin plate side electrode cap comprises an electrode cap body, a thin plate side surface (3) and a thin plate welding end surface (4), wherein the diameter of the thin plate welding end surface (4) is d2 and the radius of curvature is R1, wherein 6mm≤d2≤14mm, 40mm≤R1≤100mm; The thick plate side electrode cap comprises an electrode cap body, a thick plate side surface (8) and a thick plate welding end surface (5), wherein the diameter of the thick plate welding end surface (5) is d3 and the radius of curvature is R2, wherein d2≤d3≤14mm and R1≤R2≤100mm; Wherein, the thin plate welding end face (4) is the welding end face corresponding to the thin plate side, and the thick plate welding end face (5) is the welding end face corresponding to the thick plate side; The thin plate welding end face (4) has three rings, wherein the inner ring has a structure in the shape of a conical pit in the middle, the conical pit has a depth of h1, a diameter of d6, a diameter to the inner ring of d7, and satisfies 0.05mm≤h1≤1mm, 0.05mm≤d6≤d7≤14mm; the middle ring has a height of h3, a ring width of d4, a ring spacing of d5, the cross-sectional dimensions of each ring are equal, the cross-sectional shape is an isosceles trapezoid, the hypotenuse is 45°, and 0.05mm≤h3≤1mm, 0.05mm≤d4≤d5≤1mm; The thick plate welding end face (5) has three rings, wherein the middle of the inner ring has a structure in the shape of a conical pit, the depth of the conical pit is h2, the diameter is d10, the diameter to the inner ring is d11, and it satisfies 0.05mm≤h2≤1mm, 0.05mm≤d10≤d11≤14mm; the height of the middle ring is h4, the ring width is d8, the ring spacing is d9, the cross-sectional dimensions of each ring are equal, the cross-sectional shape is an equilateral triangle, and 0.05mm≤h4≤1mm, 0.05mm≤d8≤d9≤1mm.

2. The asymmetric ring electrode cap according to claim 1, characterized in that: The diameter of the thin plate welding end surface (4) is d2, the diameter of the thick plate welding end surface (5) is d3, and 6mm≤d2≤d3≤14mm.

3. The asymmetric ring electrode cap according to claim 1, characterized in that: The curved surface radius of the thin plate welding end surface (4) is R1, the curved surface radius of the thick plate welding end surface (5) is R2, and 40mm≤R1≤R2≤100mm.

4. A welding device for welding aluminum workpieces using the asymmetric ring electrode cap according to any one of claims 1 to 3, used for welding thin aluminum workpieces (15) and thick aluminum workpieces (14), characterized in that: include: A first welding gun arm (9) and a second welding gun arm (10); A thin plate side electrode cap (11) mounted on the first welding gun arm (9); A thick plate side electrode cap (12) mounted on the second welding gun arm (10); The thin plate aluminum workpiece (15) is made of deformed aluminum alloy and has a thickness of 0.5-2.5 mm; the thick plate aluminum workpiece (14) is made of cast aluminum or deformed aluminum alloy and has a thickness of 2.5-6 mm.

5. The welding device according to claim 4, characterized in that: During welding, the welding gun arm is operated to make the thin plate side electrode cap (11) and the thick plate side electrode cap (12) closely fit the thin plate aluminum workpiece (15) and the thick plate aluminum workpiece (14), and pressure is applied to clamp them, so that the fitting parts of the two aluminum workpieces are melted to form a molten core (16).

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